Minimal change idiopathic nephrotic syndrome (MC-INS) is a renal disorder which commonly occurs in children. The etiology and pathogenesis of MC-INS are not kn wn. Although the usual types of immunopathologic processes leading to glomerular injury cann t be demonstrated in MC-INS, severl observations suggest that MC-INS may result from the consequence of an underlying immun l gical deviation or altered immunoresponsiveness. The proposed study will examine whether the immune abnormalities in MC-INS are the result of metabolic changes that occur during the disease process. Analysis of components of the complement (C) system and metabolic turnover studies will enable further evaluation of the C abnormalities. Alteration of T-cell and B-cell immune function will be studied both in vivo and in vitro. Serum will be studied for the presence of circulating cyto- or lymphokines as evidence of increased immune responsiveness. Plasma factor(s) which may result from altered lipid metabolism, i.e., low density lipoprotein will be studied for their ability to modulate immune function. The modulating effect on T-cell function (suppression) on B-cell activity (immunoglobulin synthesis) will be studied in patients with MC-INS. A connection between impaired T-cell function in MC-INS and the C abnormalities, e.g., low C8 will be examined by testing lymphocyte-mediated lysis of C-coated target cells. Elucidation of the altered T-cell immune function C abnormalities may help clarify the bioregulatory role of altered metabolic function in disease processes. In addition, the proposed study may help define the mechanisms which play a role in the pathogenesis of MC-INS possibly lead to identification of the etiology and improve therapeutic approaches of MC-INS.